The Earth as we know it came into being around 4.5 billion years ago when gravity condensed a mass from the cloud of hot ...

Encountering Neptune in 1989, NASA's Voyager mission completed humankind's first close-up exploration of the four giant outer ...

Both the star and its planet(s) orbit the shared center of mass between them. Because the star contains the bulk of the system's mass, the center of mass is found within the star — but ...